High lift control systems for modern aircraft typically comprise one or more moveable leading edge slats and/or one or more moveable trailing edge flaps located on each wing of the aircraft. The slats and flaps are aerodynamic surfaces that, when deployed or extended out from the respective edge of the wing, produce a relatively higher coefficient of lift for the aircraft. Some aircraft have both slats and flaps while other aircraft have only flaps. This increased lift allows the aircraft to be flown at slower speeds, thereby allowing the aircraft to take-off and land in shorter distances (i.e., on shorter runways). On the other hand, at aircraft cruise altitudes the slats and flaps are typically not deployed and are, thus, held in their retracted or stowed positions.
The high lift surfaces (e.g., slats and flaps) are typically held in their retracted positions and in various deployed positions by mechanical actuators, which are each driven by a central power drive unit via a mechanical driveline. A moveable high lift selector lever in the cockpit (e.g., in the center pedestal) allows the pilot or co-pilot to select a desired high lift configuration (i.e., a particular angular position of the slats and flaps). The lever typically has a number of discrete detent positions, as the lever is moved or extended aft or rearward when it is desired to land the aircraft from a cruising in-flight phase. The discrete detent positions of the lever are sensed by one or more sensors, which convert the lever positions to variable electrical signals. These signals are read by one or more control computers. In reponse to changes in the lever position, the control computer commands the power drive units to drive the actuators and hence the slats and/or flaps to new positions with respect to the wings. For each discrete detent position of the lever, there typically is a unique angular position of the slats and/or flaps with respect to the corresponding wing.
Also, when moving the high lift selector lever in the opposite, retract or fore direction when it is desired to effect a take-off of the aircraft to ultimately achieve a cruise condition of the aircraft, the lever is again typically moved into some or all of the discrete detent positions. There may not be as many such discrete detent positions of the lever needed in this retract direction in order to have the aircraft go from take-off to cruise. Nevertheless, for each discrete detent position of the lever in this take-off direction, typically in the prior art the slats and/or flaps are in the same angular position as they are in the opposite extending aft direction of the lever. This is so for certain exemplary embodiments of a high lift selector lever that moves in two different opposite directions. Other types of high lift selector levers may be utilized that operate in a manner different from simply two opposite directions.
Problems with this type of known, conventional high lift control system for aircraft include the fact that there typically exist a limited number of unique positions of the slats and/or flaps due to the limited number of different discrete mechanical positions of the high lift selector lever. Modern aircraft typically have a high lift selector lever that has anywhere from four to nine discrete mechanical positions. Oftentimes the number of lever positions depends on the physical space available in the center pedestal of the cockpit to accommodate a desired physical size for the high lift selector lever.
When it is desired to increase the take-off and landing performance of the aircraft by increasing the number of high lift positions of the slats and/or flaps, one possible solution is to increase the number of discrete, physical mechanical positions of the high lift selector lever. However, problems with this approach include the fact that such a lever having more discrete positions results in a larger flap lever assembly to maintain a suitable separation between each discrete lever position. Also, there exists a human performance factor impact in the form of geometric and ergonomic factors (e.g., reduced proprioceptive cues) along with various cognitive factors (e.g., increased attention, increased memory load, time and opportunity for error, and increased cognitive and visual complexity). Thus, increasing the number of discrete, physical mechanical positions of the high lift selector lever is not a desirable solution to increasing the take-off and landing performance of the aircraft.
What is needed is an improved high lift control system for aircraft which limits the number of discrete physical mechanical positions of the high lift selector lever, while at the same time increasing the number of high lift positions of the slats and/or flaps.